Wi-Fi signaling by cellular devices for coexistence in unlicensed frequency bands

ABSTRACT

This disclosure relates to Wi-Fi signaling in conjunction with cellular communication in unlicensed frequency bands for efficient co-existence. According to one embodiment, a cell may be established between a cellular base station and a wireless user equipment device on a frequency channel in an unlicensed frequency band. A cellular communication may be scheduled between the base station and the user equipment device. A Wi-Fi signal may be transmitted on the frequency channel in conjunction with the scheduled cellular communication. The Wi-Fi signal may indicate a length of the scheduled cellular communication using Wi-Fi signaling. The scheduled cellular communication may be performed via the cell.

PRIORITY CLAIM

The present application is a continuation of U.S. patent applicationSer. No. 14/610,426, filed Jan. 30, 2015, which claims benefit ofpriority to U.S. Provisional Application No. 61/936,057 titled “Wi-FiSignaling by Cellular Devices for Coexistence in Unlicensed FrequencyBands” and filed on Feb. 5, 2014, which are hereby incorporated byreference in their entirety as though fully and completely set forthherein.

FIELD

The present application relates to wireless devices, and moreparticularly to a system and method for cellular devices to use Wi-Fisignaling in conjunction with cellular communication when performingwireless communication in unlicensed frequency bands.

DESCRIPTION OF THE RELATED ART

Wireless communication systems are rapidly growing in usage.Additionally, there exist numerous different wireless communicationtechnologies and standards. Some examples of wireless communicationstandards include GSM, UMTS (associated with, for example, WCDMA orTD-SCDMA air interfaces), LTE, LTE Advanced (LTE-A), HSPA, 3GPP2CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), IEEE 802.11 (WLAN orWi-Fi), IEEE 802.16 (WiMAX), Bluetooth, and others.

In some wireless communication systems, such as certain cellularcommunication networks, wireless communication is performed on frequencybands which have been licensed (e.g., by a cellular network provider).Additionally, in some wireless communication systems, such as Wi-Fi andBluetooth wireless communication systems, wireless communication isperformed on unlicensed frequency bands, such as the 2.4 GHz ISMfrequency band.

SUMMARY

Embodiments are presented herein of methods for cellular devices to useWi-Fi signaling in conjunction with cellular communication whenperforming wireless communication in unlicensed frequency bands, and ofdevices configured to implement the methods.

Since Wi-Fi networks may commonly be deployed on unlicensed frequencybands, this should be accounted for when considering using cellularcommunication on an unlicensed frequency band. Use of Wi-Fi signalingaccording to the techniques described herein may represent one possiblemechanism to improve coexistence characteristics between cellular andWi-Fi communication technologies in unlicensed frequency bands.

According to the techniques described herein, a cellular device (e.g.,user equipment devices, base stations, etc.) may also be equipped withWi-Fi communication capabilities. For example, as one possibility an LTEeNodeB might be equipped with a Wi-Fi access point transceiver andbaseband chip, enabling it to act as a Wi-Fi access point. As anotherexample, a user device might be equipped with each of cellular radio andWi-Fi radio communication capabilities.

In conjunction with scheduling a cellular communication between suchcellular devices on a frequency channel in an unlicensed frequency band,one or both of those devices may use Wi-Fi signaling to indicate alength of the scheduled cellular communication. For example, the devicemay utilize its Wi-Fi capabilities to transmit a Wi-Fi preamble and oneor more Wi-Fi headers (such as a Wi-Fi PHY layer SIG field) on thefrequency channel, which may indicate a transmission length or durationas if the device were performing a Wi-Fi transmission on the frequencychannel. Note that the Wi-Fi capabilities of the cellular device (e.g.,UE or BS) may be provided by separate Wi-Fi circuitry, or in someinstances may be provided by the cellular (e.g., LTE) circuitry of thedevice. For example, the cellular circuitry may be configured togenerate and transmit the Wi-Fi signaling as part of being configured toperform cellular communication in unlicensed frequency bands.

The cellular device may, however, cease transmitting Wi-Fi signals afterindicating the transmission length, e.g., to avoid interfering with itsown cellular transmission, and may instead perform the scheduledcellular communication. Any Wi-Fi devices receiving such the Wi-Fisignals may have noted the indicated duration of the transmission, and(e.g., according to a carrier sensing collision avoidance algorithm)refrain from performing Wi-Fi communication for the indicated duration.Thus, the likelihood that Wi-Fi transmissions interfering with thecellular communication on the frequency channel will be performed may begreatly reduced.

It should be noted that Wi-Fi devices may also benefit from such atechnique being performed by cellular devices operating in the same (oran overlapping) frequency channel. For example, without the Wi-Fisignaling in conjunction with the cellular communication, a Wi-Fi devicemight attempt a Wi-Fi transmission during the cellular communication,which might not only cause interference to the cellular communication,but also be subject to interference from the cellular communication,which might potentially cause the Wi-Fi transmission to fail. Accordingto the techniques described herein, however, the Wi-Fi device mayinstead conserve power by refraining from attempting to transmit at atime when the medium is not actually free. Thus, the techniquesdescribed herein may (at least in some instances) be beneficial toCellular-Wi-Fi coexistence from the perspective of both wirelesscommunication technologies.

It should be noted that a variety of implementation details of thetechniques described herein may be possible. For example, as will befurther described herein subsequently, such Wi-Fi signaling may beperformed prior to or simultaneously with the associated cellularcommunication, according to various embodiments. As an additionalexample, such Wi-Fi signaling may be used in the case of carrieraggregation (e.g., such that scheduling communications for a cell in anunlicensed frequency band are performed on a different cell (which mightbe in a licensed frequency band)), or in the case of a standalone celldeployed in an unlicensed frequency band (e.g., such that schedulingcommunications for the cell are performed on the cell itself).

The techniques described herein may be implemented in and/or used with anumber of different types of devices, including but not limited tocellular base stations, cellular phones, tablet computers, wearablecomputing devices, portable media players, and any of various othercomputing devices.

This Summary is intended to provide a brief overview of some of thesubject matter described in this document. Accordingly, it will beappreciated that the above-described features are merely examples andshould not be construed to narrow the scope or spirit of the subjectmatter described herein in any way. Other features, aspects, andadvantages of the subject matter described herein will become apparentfrom the following Detailed Description, Figures, and Claims.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present subject matter can be obtainedwhen the following detailed description of the embodiments is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates an exemplary (and simplified) wireless communicationsystem, according to some embodiments;

FIG. 2 illustrates a base station (BS) in communication with a userequipment (UE) device, according to some embodiments;

FIG. 3 illustrates an exemplary block diagram of a UE, according to someembodiments;

FIG. 4 illustrates an exemplary block diagram of a BS, according to someembodiments;

FIG. 5 illustrates an exemplary carrier aggregation scheme, according tosome embodiments;

FIG. 6 illustrates an exemplary cross-carrier scheduling scheme,according to some embodiments;

FIG. 7 is a communication flow diagram illustrating an exemplary methodfor using Wi-Fi signaling in conjunction with cellular communication inunlicensed frequency bands, according to some embodiments;

FIG. 8 illustrates an exemplary LTE-U access point with a Wi-Ficapability module, according to some embodiments;

FIGS. 9-10 illustrate possible transmission schemes for using Wi-Fisignaling in conjunction with cellular communication in unlicensedfrequency bands, according to some embodiments;

FIG. 11 illustrates an exemplary coexistence interface between LTE andWi-Fi in a wireless device, according to some embodiments; and

FIGS. 12-16 illustrate exemplary aspects of Wi-Fi communication,according to some embodiments.

While the features described herein may be susceptible to variousmodifications and alternative forms, specific embodiments thereof areshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the drawings and detaileddescription thereto are not intended to be limiting to the particularform disclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the subject matter as defined by the appended claims.

DETAILED DESCRIPTION

Terms

The following is a glossary of terms used in this disclosure:

Memory Medium—Any of various types of non-transitory memory devices orstorage devices. The term “memory medium” is intended to include aninstallation medium, e.g., a CD-ROM, floppy disks, or tape device; acomputer system memory or random access memory such as DRAM, DDR RAM,SRAM, EDO RAM, Rambus RAM, etc.; a non-volatile memory such as a Flash,magnetic media, e.g., a hard drive, or optical storage; registers, orother similar types of memory elements, etc. The memory medium mayinclude other types of non-transitory memory as well or combinationsthereof. In addition, the memory medium may be located in a firstcomputer system in which the programs are executed, or may be located ina second different computer system which connects to the first computersystem over a network, such as the Internet. In the latter instance, thesecond computer system may provide program instructions to the firstcomputer for execution. The term “memory medium” may include two or morememory mediums which may reside in different locations, e.g., indifferent computer systems that are connected over a network. The memorymedium may store program instructions (e.g., embodied as computerprograms) that may be executed by one or more processors.

Carrier Medium—a memory medium as described above, as well as a physicaltransmission medium, such as a bus, network, and/or other physicaltransmission medium that conveys signals such as electrical,electromagnetic, or digital signals.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

User Equipment (UE) (or “UE Device”)—any of various types of computersystems devices which are mobile or portable and which performs wirelesscommunications. Examples of UE devices include mobile telephones orsmart phones (e.g., iPhone™, Android™-based phones), portable gamingdevices (e.g., Nintendo DS™, PlayStation Portable™, Gameboy Advance™,iPhone™), laptops, wearable devices (e.g., smart watch, smart glasses),PDAs, portable Internet devices, music players, data storage devices, orother handheld devices, etc. In general, the term “UE” or “UE device”can be broadly defined to encompass any electronic, computing, and/ortelecommunications device (or combination of devices) which is easilytransported by a user and capable of wireless communication.

Base Station—The term “Base Station” has the full breadth of itsordinary meaning, and at least includes a wireless communication stationinstalled at a fixed location and used to communicate as part of awireless telephone system or radio system.

Processing Element—refers to various elements or combinations ofelements. Processing elements include, for example, circuits such as anASIC (Application Specific Integrated Circuit), portions or circuits ofindividual processor cores, entire processor cores, individualprocessors, programmable hardware devices such as a field programmablegate array (FPGA), and/or larger portions of systems that includemultiple processors.

Channel—a medium used to convey information from a sender (transmitter)to a receiver. It should be noted that since characteristics of the term“channel” may differ according to different wireless protocols, the term“channel” as used herein may be considered as being used in a mannerthat is consistent with the standard of the type of device withreference to which the term is used. In some standards, channel widthsmay be variable (e.g., depending on device capability, band conditions,etc.). For example, LTE may support scalable channel bandwidths from 1.4MHz to 20 MHz. In contrast, WLAN channels may be 22 MHz wide whileBluetooth channels may be 1 Mhz wide. Other protocols and standards mayinclude different definitions of channels. Furthermore, some standardsmay define and use multiple types of channels, e.g., different channelsfor uplink or downlink and/or different channels for different uses suchas data, control information, etc.

Band—The term “band” has the full breadth of its ordinary meaning, andat least includes a section of spectrum (e.g., radio frequency spectrum)in which channels are used or set aside for the same purpose.

Automatically—refers to an action or operation performed by a computersystem (e.g., software executed by the computer system) or device (e.g.,circuitry, programmable hardware elements, ASICs, etc.), without userinput directly specifying or performing the action or operation. Thusthe term “automatically” is in contrast to an operation being manuallyperformed or specified by the user, where the user provides input todirectly perform the operation. An automatic procedure may be initiatedby input provided by the user, but the subsequent actions that areperformed “automatically” are not specified by the user, i.e., are notperformed “manually”, where the user specifies each action to perform.For example, a user filling out an electronic form by selecting eachfield and providing input specifying information (e.g., by typinginformation, selecting check boxes, radio selections, etc.) is fillingout the form manually, even though the computer system must update theform in response to the user actions. The form may be automaticallyfilled out by the computer system where the computer system (e.g.,software executing on the computer system) analyzes the fields of theform and fills in the form without any user input specifying the answersto the fields. As indicated above, the user may invoke the automaticfilling of the form, but is not involved in the actual filling of theform (e.g., the user is not manually specifying answers to fields butrather they are being automatically completed). The presentspecification provides various examples of operations beingautomatically performed in response to actions the user has taken.

IEEE 802.11—refers to technology based on IEEE 802.11 wireless standardssuch as 802.11a, 802.11.b, 802.11g, 802.11n, 802.11-2012, 802.11ac,and/or other IEEE 802.11 standards. IEEE 802.11 technology may also bereferred to as “Wi-Fi” or “wireless local area network (WLAN)”technology.

FIGS. 1 and 2—Communication System

FIG. 1 illustrates an exemplary (and simplified) wireless communicationsystem, according to some embodiments. It is noted that the system ofFIG. 1 is merely one example of a possible system, and embodiments maybe implemented in any of various systems, as desired.

As shown, the exemplary wireless communication system includes a basestation 102A which communicates over a transmission medium with one ormore user devices 106A, 106B, etc., through 106N. Each of the userdevices may be referred to herein as a “user equipment” (UE). Thus, theuser devices 106 are referred to as UEs or UE devices.

The base station 102A may be a base transceiver station (BTS) or cellsite, and may include hardware that enables wireless communication withthe UEs 106A through 106N. The base station 102A may also be equipped tocommunicate with a network 100 (e.g., a core network of a cellularservice provider, a telecommunication network such as a public switchedtelephone network (PSTN), and/or the Internet, among variouspossibilities). Thus, the base station 102A may facilitate communicationbetween the user devices and/or between the user devices and the network100.

The communication area (or coverage area) of the base station may bereferred to as a “cell.” The base station 102A and the UEs 106 may beconfigured to communicate over the transmission medium using any ofvarious radio access technologies (RATs), also referred to as wirelesscommunication technologies, or telecommunication standards, such as GSM,UMTS (WCDMA, TD-SCDMA), LTE, LTE-Advanced (LTE-A), HSPA, 3GPP2 CDMA2000(e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), Wi-Fi, WiMAX etc.

Base station 102A and other similar base stations (such as base stations102B . . . 102N) operating according to the same or a different cellularcommunication standard may thus be provided as a network of cells, whichmay provide continuous or nearly continuous overlapping service to UEs106A-N and similar devices over a wide geographic area via one or morecellular communication standards.

Thus, while base station 102A may act as a “serving cell” for UEs 106A-Nas illustrated in FIG. 1, each UE 106 may also be capable of receivingsignals from (and possibly within communication range of) one or moreother cells (which might be provided by base stations 102B-N and/or anyother base stations), which may be referred to as “neighboring cells”.Such cells may also be capable of facilitating communication betweenuser devices and/or between user devices and the network 100, accordingto the same wireless communication technology as base station 102Aand/or any of various other possible wireless communicationtechnologies. Such cells may include “macro” cells, “micro” cells,“pico” cells, and/or cells which provide any of various othergranularities of service area size. For example, base stations 102A-Billustrated in FIG. 1 might be macro cells, while base station 102Nmight be a micro cell. Other configurations are also possible.

Note that a UE 106 may be capable of communicating using multiplewireless communication standards. For example, a UE 106 may beconfigured to communicate using a wireless networking (e.g., Wi-Fi)and/or peer-to-peer wireless communication protocol (e.g., BT, Wi-Fipeer-to-peer, etc.) in addition to at least one cellular communicationprotocol (e.g., GSM, UMTS (WCDMA, TD-SCDMA), LTE, LTE-A, HSPA, 3GPP2CDMA2000 (e.g., 1×RTT, 1×EV-DO, HRPD, eHRPD), etc.). The UE 106 may alsoor alternatively be configured to communicate using one or more globalnavigational satellite systems (GNSS, e.g., GPS or GLONASS), one or moremobile television broadcasting standards (e.g., ATSC-M/H or DVB-H),and/or any other wireless communication protocol, if desired. Othercombinations of wireless communication standards (including more thantwo wireless communication standards) are also possible.

FIG. 2 illustrates user equipment 106 (e.g., one of the devices 106Athrough 106N) in communication with a base station 102 (e.g., one of thebase stations 102A through 102N), according to some embodiments. The UE106 may be a device with cellular communication capability such as amobile phone, a hand-held device, a wearable device, a computer or atablet, or virtually any type of wireless device.

The UE 106 may include a processor that is configured to execute programinstructions stored in memory. The UE 106 may perform any of the methodembodiments described herein by executing such stored instructions.Alternatively, or in addition, the UE 106 may include a programmablehardware element such as an FPGA (field-programmable gate array) that isconfigured to perform any of the method embodiments described herein, orany portion of any of the method embodiments described herein.

The UE 106 may include one or more antennas for communicating using oneor more wireless communication protocols or technologies. In oneembodiment, the UE 106 might be configured to communicate using eitherof CDMA2000 (1×RTT/1×EV-DO/HRPD/eHRPD) or LTE using a single sharedradio and/or GSM or LTE using the single shared radio. The shared radiomay couple to a single antenna, or may couple to multiple antennas(e.g., for MIMO) for performing wireless communications. In general, aradio may include any combination of a baseband processor, analog RFsignal processing circuitry (e.g., including filters, mixers,oscillators, amplifiers, etc.), or digital processing circuitry (e.g.,for digital modulation as well as other digital processing). Similarly,the radio may implement one or more receive and transmit chains usingthe aforementioned hardware. For example, the UE 106 may share one ormore parts of a receive and/or transmit chain between multiple wirelesscommunication technologies, such as those discussed above.

In some embodiments, the UE 106 may include separate (and possiblymultiple) transmit and/or receive chains (e.g., including separate RFand/or digital radio components) for each wireless communicationprotocol with which it is configured to communicate. As a furtherpossibility, the UE 106 may include one or more radios which are sharedbetween multiple wireless communication protocols, and one or moreradios which are used exclusively by a single wireless communicationprotocol. For example, the UE 106 might include a shared radio forcommunicating using either of LTE or 1×RTT (or LTE or GSM), and separateradios for communicating using each of Wi-Fi and Bluetooth. Otherconfigurations are also possible.

FIG. 3—Exemplary Block Diagram of a UE

FIG. 3 illustrates an exemplary block diagram of a UE 106, according tosome embodiments. As shown, the UE 106 may include a system on chip(SOC) 300, which may include portions for various purposes. For example,as shown, the SOC 300 may include processor(s) 302 which may executeprogram instructions for the UE 106 and display circuitry 304 which mayperform graphics processing and provide display signals to the display360. The processor(s) 302 may also be coupled to memory management unit(MMU) 340, which may be configured to receive addresses from theprocessor(s) 302 and translate those addresses to locations in memory(e.g., memory 306, read only memory (ROM) 350, NAND flash memory 310)and/or to other circuits or devices, such as the display circuitry 304,wireless communication circuitry 330, connector I/F 320, and/or display360. The MMU 340 may be configured to perform memory protection and pagetable translation or set up. In some embodiments, the MMU 340 may beincluded as a portion of the processor(s) 302.

As shown, the SOC 300 may be coupled to various other circuits of the UE106. For example, the UE 106 may include various types of memory (e.g.,including NAND flash 310), a connector interface 320 (e.g., for couplingto a computer system, dock, charging station, etc.), the display 360,and wireless communication circuitry (e.g., radio) 330 (e.g., for LTE,Wi-Fi, GPS, etc.).

The UE device 106 may include at least one antenna (and possiblymultiple antennas, e.g., for MIMO and/or for implementing differentwireless communication technologies, among various possibilities), forperforming wireless communication with base stations and/or otherdevices. For example, the UE device 106 may use antenna(s) 335 toperform the wireless communication. As noted above, the UE 106 may beconfigured to communicate wirelessly using multiple wirelesscommunication technologies in some embodiments.

As described further subsequently herein, the UE 106 may includehardware and software components for implementing features for usingWi-Fi signaling or new signaling (e.g., derived from WiFi signaling) inconjunction with cellular communication when performing wirelesscommunication in unlicensed frequency bands, such as those describedherein with reference to, inter alia, FIG. 7. The processor 302 of theUE device 106 may be configured to implement part or all of the methodsdescribed herein, e.g., by executing program instructions stored on amemory medium (e.g., a non-transitory computer-readable memory medium).In other embodiments, processor 302 may be configured as a programmablehardware element, such as an FPGA (Field Programmable Gate Array), or asan ASIC (Application Specific Integrated Circuit). Alternatively (or inaddition) the processor 302 of the UE device 106, in conjunction withone or more of the other components 300, 304, 306, 310, 320, 330, 335,340, 350, 360 may be configured to implement part or all of the featuresdescribed herein, such as the features described herein with referenceto, inter alia, FIG. 7.

FIG. 4—Exemplary Block Diagram of a Base Station

FIG. 4 illustrates an exemplary block diagram of a base station 102,according to some embodiments. It is noted that the base station of FIG.4 is merely one example of a possible base station. As shown, the basestation 102 may include processor(s) 404 which may execute programinstructions for the base station 102. The processor(s) 404 may also becoupled to memory management unit (MMU) 440, which may be configured toreceive addresses from the processor(s) 404 and translate thoseaddresses to locations in memory (e.g., memory 460 and read only memory(ROM) 450) or to other circuits or devices.

The base station 102 may include at least one network port 470. Thenetwork port 470 may be configured to couple to a telephone network andprovide a plurality of devices, such as UE devices 106, access to thetelephone network as described above in FIGS. 1 and 2.

The network port 470 (or an additional network port) may also oralternatively be configured to couple to a cellular network, e.g., acore network of a cellular service provider. The core network mayprovide mobility related services and/or other services to a pluralityof devices, such as UE devices 106. In some cases, the network port 470may couple to a telephone network via the core network, and/or the corenetwork may provide a telephone network (e.g., among other UE devicesserviced by the cellular service provider).

The base station 102 may include at least one antenna 434, and possiblymultiple antennas. The antenna(s) 434 may be configured to operate as awireless transceiver and may be further configured to communicate withUE devices 106 via radio 430. The antenna 434 communicates with theradio 430 via communication chain 432. Communication chain 432 may be areceive chain, a transmit chain or both. The radio 430 may be configuredto communicate via various wireless telecommunication standards,including, but not limited to, LTE, LTE-A, UMTS, CDMA2000, Wi-Fi, etc.

The BS 102 may be configured to communicate wirelessly using multiplewireless communication standards. In some instances, the base station102 may include multiple radios, which may enable the base station 102to communicate according to multiple wireless communicationtechnologies. For example, as one possibility, the base station 102 mayinclude an LTE radio for performing communication according to LTE(TDD-FDD), LTE in unlicensed spectrum (TDD-FDD) as well as a Wi-Fi radiofor performing communication according to Wi-Fi. In such a case, thebase station 102 may be capable of operating as both an LTE base stationand a Wi-Fi access point. As another possibility, the base station 102may include a multi-mode radio which is capable of performingcommunications according to any of multiple wireless communicationtechnologies (e.g., LTE and Wi-Fi).

Such capabilities may be particularly useful for managing interferenceand coordinating communication on unlicensed frequency bands, e.g., onwhich wireless communication according to multiple wirelesscommunication technologies may be possible (and possibly even common),which the BS 102 may be configured to do. For example, as describedfurther subsequently herein, the BS 102 may include hardware andsoftware components for implementing features for using Wi-Fi signalingor any other (e.g., hybrid LTE-Wi-Fi) preamble in conjunction withcellular communication when performing wireless communication inunlicensed frequency bands, such as those described herein withreference to, inter alia, FIG. 7. The processor 404 of the base station102 may be configured to implement part or all of the methods describedherein, e.g., by executing program instructions stored on a memorymedium (e.g., a non-transitory computer-readable memory medium).Alternatively, the processor 404 may be configured as a programmablehardware element, such as an FPGA (Field Programmable Gate Array), or asan ASIC (Application Specific Integrated Circuit), or a combinationthereof. Alternatively (or in addition) the processor 404 of the BS 102,in conjunction with one or more of the other components 430, 432, 434,440, 450, 460, 470 may be configured to implement part or all of thefeatures described herein, such as the features described herein withreference to, inter alia, FIG. 7.

FIG. 5—Carrier Aggregation

Carrier aggregation is a scheme in which multiple carriers (e.g.,frequency channels) may be used for wireless communication with a UEaccording to a wireless communication technology. FIG. 5 illustrates oneexemplary carrier aggregation scheme (e.g., which may be used inaccordance with the LTE radio access technology) which may be used inaccordance with other aspects of this disclosure, such as with respectto the method of FIG. 7.

In the illustrated scheme, up to five component carriers (carriers 504,506, 508, 510, 512) may be aggregated for a single user device (such oneof the UEs 106 illustrated in and described with respect to FIGS. 1-3).Each component carrier may use a channel width of up to 20 MHz. As onepossibility, each component carrier may be an LTE release 10 carrier.Thus, according to the exemplary scheme, a UE may be allocated up to 100MHz of bandwidth. In many instances, such a carrier aggregation schememay enable a UE participating in it with greater throughput than withoutsuch a scheme.

In many cases, component carriers may utilize adjacent frequencychannels. However, it should be noted that it is also possible toimplement carrier aggregation utilizing non-continuous frequencychannels, potentially including non-continuous frequency channels withinthe same frequency band, and/or frequency channels within differentfrequency bands. For example, it may be possible to implement carrieraggregation using a frequency channel in a licensed frequency band asone component carrier, and a frequency channel in an unlicensedfrequency band as another component carrier.

It should be noted that while the exemplary scheme illustrated in FIG. 5and the associated description are provided by way of example as onepossible manner of implementing carrier aggregation, they are notintended to be limiting to the disclosure as a whole. Numerousalternatives to and variations of the details thereof are possible andshould be considered within the scope of the present disclosure. Forexample: carrier aggregation schemes may be implemented in conjunctionwith other wireless communication technologies; carriers according toother LTE releases or other radio access technologies altogether may beused; carriers having different channel widths may be used; differentnumbers of component carriers may be supported; and/or any of numerousother alternatives to and variations of the illustrated scheme are alsopossible.

FIG. 6—Cross-Carrier Scheduling

For systems which implement carrier aggregation, various controlschemes/mechanisms are possible. As one possibility, an independent cellmay be implemented on each component carrier, for example by providing acontrol channel with data scheduling and other control features for eachcell on the component carrier for that cell. As another possibility,some or all control functions may be centralized. For example, a“primary cell” might be implemented on one (“primary”) componentcarrier, while “secondary cells” might be implemented on any additional(“secondary”) component carriers, such that some or all controlinformation for the secondary cells is communicated by way of theprimary cell.

Such a scheme may be referred to as “cross-carrier scheduling”, and FIG.6 illustrates one such exemplary scheme (e.g., which may be used inaccordance with the LTE radio access technology). It should be notedthat while the exemplary scheme illustrated in FIG. 6 and the associateddescription are provided by way of example as one possible manner ofimplementing a cross-carrier scheduling mechanism, they are not intendedto be limiting to the disclosure as a whole. Numerous alternatives toand variations of these exemplary details are possible and should beconsidered within the scope of the present disclosure.

As shown, in the exemplary scheme a user device (e.g., a UE 106 such asillustrated in and described with respect to FIGS. 1-3) may have threeactive carriers as part of its connection to a network (e.g., by way ofone or more base stations 102 such as illustrated in and described withrespect to FIGS. 1-2 and 4), which may be implemented as a primary cell602 and two secondary cells 604, 606. The network may provide controldata 608 (e.g., for scheduling user data communications, performingmobility related functions, etc.) for all three cells by way of acontrol channel of the primary cell 602. For example, the control data608 may be communicated by way of a physical downlink control channel(PDCCH) of the primary cell 602.

The network may provide user data 610 (e.g., application data fornetworking applications such as web browser applications, emailapplications voice call applications, video chat applications, gameapplications, etc.) to the UE 106 on any or all of the cells 602, 604,606. For example, various portions of the user data 610 may becommunicated by way of a physical downlink shared channel (PDSCH) ofeach of the primary cell 602 and the secondary cells 604, 606.

Thus, cross-carrier scheduling may be used in conjunction with carrieraggregation to centralize (at least a portion of) control communicationson one cell. This technique may be used in many instances forinfrastructure mode communications between a UE and a network, such asillustrated in the exemplary scheme of FIG. 6. Such a technique may beparticularly useful if different component carriers are known and/orexpected to have different interference levels, since in such a case thecarrier having the lowest interference level may advantageously be usedfor high priority control data. Such a situation may be the case, forexample, if one component carrier is on a licensed frequency band forwhich the potential for interference is substantially limited to thatcaused by network controlled wireless communication, while anothercomponent carrier is on an unlicensed frequency band which may besubject to interference caused by wireless communication which is notunder network control.

FIG. 7—Communication Flow Diagram

FIG. 7 is a communication/signal flow diagram illustrating ascheme/method for supporting efficient coexistence between LTE and Wi-Ficommunications in unlicensed frequency bands. Aspects of the method ofFIG. 7 may be implemented by a BS 102 (e.g., such as illustrated in anddescribed with respect to FIGS. 1-2 and 4), and by a UE 106 (e.g., suchas illustrated in and described with respect to FIGS. 1-3), or moregenerally in conjunction with any of the computer systems or devicesshown in the above Figures, among other devices, as desired.

In various embodiments, some of the elements of the method shown may beperformed concurrently, in a different order than shown, or may beomitted. Additional elements may also be performed as desired. As shown,the method may operate as follows.

In 702, a cell may be established on a frequency channel in anunlicensed frequency band. The cell may be established between acellular base station (BS) and a wireless user equipment (UE) device.The cell may be established according to a first wireless communicationtechnology (or “radio access technology” or “RAT”), such as LTE.

The cell may be a stand-alone cell, or may be a cell formed as part of acarrier-aggregation communication link between the BS and the UE. In thecase of a stand-alone cell, both control communications and datacommunications for the cell may be performed communications on thefrequency channel on which the cell is established.

If the cell is formed as part of a carrier aggregation communicationlink, it may be the case that the cell is a “secondary carrier” or“secondary cell”, which may be formed in addition to (e.g., subsequentto) a “primary carrier” or “primary cell”.

For example, a primary carrier may be established (e.g., configured)between the BS and the UE. The primary carrier may also be establishedaccording to the first wireless communication technology. The primarycarrier may be established on a frequency channel in a licensedfrequency band, which may also be referred to herein as a “firstfrequency band”. For example, a cellular network provider may havelicensed a particular frequency band (possibly specifically for use inconjunction with a particular radio access technology, such as LTE-A,LTE, WCDMA, CDMA2000, GSM, etc.), and may provide a cellular networkwhich operates primarily within that licensed frequency band. Such alicensed frequency band may be subject to less external interferencethan the unlicensed frequency band. For example, the unlicensedfrequency band might be subject to interference from other wirelesscommunication technologies and/or from other cellular network operatorsutilizing a similar or the same wireless communication technology in theunlicensed frequency band, whereas a licensed frequency band may not besubject to such external interference sources, e.g., if the licensedfrequency band is licensed for the exclusive use of one particularcellular network provider.

In such a case, the primary carrier may provide the UE with aninfrastructure mode type communication link to a cellular network. Thus,the primary carrier may provide a connection to a core network, e.g., ofa cellular service provider, with which a user of the UE may have asubscription and/or other agreement to provide cellular service. Thecellular network may thus provide connectivity between the user deviceand various services and/or devices coupled to the cellular network,such as other user devices, a public switched telephone network, theInternet, various cloud-based services, etc. The primary carrier may beused for control communications between the UE and the BS in such acase, if desired, and may also be used for data (e.g., user data)communications.

Note that as part of such a cellular network, the BS may operate inconjunction with numerous other base stations (which may provide othercells) and other network hardware and software to provide continuous (ornearly continuous) overlapping wireless service over a wide geographicarea. At least in some instances, the UE may select a cell with the BSto establish as the primary cell from among multiple cells withinwireless communication range of the UE, which may be provided by nearbybase stations. For example, the UE may be capable of discovering,detecting signals from, and possibly communicating with some or all ofmultiple neighboring cells, e.g., depending on signal strength/quality,permission, technological interoperability, etc. The primary cell may beselected and configured/established on the basis of one or more signalstrength and/or signal quality measurements of the primary cell and/orother nearby cells, among other possible criteria (e.g., wirelesstraffic congestion of the cell(s), operator of the cell(s), wirelesstechnology according to which the cell(s) operate, etc.).

Note further that cell selection may be an initial cell selection, e.g.,upon powering on the UE 106 (or possibly after powering on a radio ofthe UE, e.g., upon exiting a limited-operation or “airplane mode”),according to some embodiments. Alternatively, the cell selection may bepart of a cell re-selection procedure. For example, the UE might performa cell re-selection procedure to select a new cell with better signalstrength and/or quality as a primary cell based on experiencing degradedsignal strength and/or quality on a previous primary cell, e.g., as aresult of moving from a service area of the previous primary cell to aservice area of the new primary cell.

Establishing the cell on the unlicensed frequency band may includescanning channels of the unlicensed (“second”) frequency band, (whichmay be an industrial-scientific-medical (ISM) frequency band, as oneexample), e.g., for interference. As previously noted, since unlicensedfrequency bands may be subject to interference from other wirelesscommunication (e.g., potentially from one or more other wirelesscommunication technologies) which is not under network control, it maybe desirable to determine how much interference is currently present oneach of the channels in the unlicensed frequency band prior to selectingone for use as a carrier.

In particular, at least in some instances it may be desirable to checkfor Wi-Fi interference, e.g., if the unlicensed frequency band is one inwhich Wi-Fi communication is known to be performed. Thus the BS (or theWi-Fi device controlled by and/or coupled to the BS) may scan one ormore channels (e.g., Wi-Fi and/or radar channels) on the unlicensedfrequency band. The BS may be equipped with (or coupled to and incontrol of) Wi-Fi and hybrid Wi-Fi/cellular communication circuitry(e.g., may be configured to act as a Wi-Fi access point, or may becoupled to and control a Wi-Fi access point, or may include a hybridWi-Fi/cellular module enabling hybrid signaling) specifically for such apurpose (and/or for other purposes), if desired. Scanning the channelsmay include measuring any of various channel condition metrics and/ormetrics which may be used to gauge or infer interference levels, such asRSSI. As one possibility, the BS may perform power spectrum densitydetection on such an unlicensed frequency band. As a furtherpossibility, the BS may detect energy in a particular channel by usingits RF front end, such that the energy detetion is agnostic of thetechnology used in that particular channel. In such a case, as long asthe energy (RSSI) detected is higher than a certain threshold (e.g.RSSI>−80 dBm, or any other desired threshold) then the particularchannel (ISM frequency) may be assumed to be occupied (i.e.,non-interference free).

Based on scanning the (e.g., Wi-Fi) channels in the unlicensed frequencyband, the BS may select one or more channels (e.g., Wi-Fi channels, orother unlicensed spectrum channels according to the first wirelesscommunication technology (such as LTE channels) which maycorrespond/overlap in frequency with one or more of the Wi-Fi channels)in the unlicensed frequency band as potential channels on which toestablish a carrier. The selected channel(s) may be those on which Wi-Fiinterference has been determined to be less likely and/or prevalent,such as channels for which RSSI are below a desired threshold.

Having selected one or more channels as potential carriers for the cellin the unlicensed frequency band, the BS may provide an indication ofsuch channels to the UE. For example, the BS may generate and provide alist of potential channels in the unlicensed frequency band to the UE ina configuration message (e.g., an RRC configuration object) via theprimary cell, in a carrier aggregation scenario. The UE may store such alist of potential channels and configure each channel on the list as apotential carrier, though each remain ‘inactive’ and unused as an actualcarrier until more explicitly activated.

The UE may additionally provide feedback to the BS (e.g., via theprimary cell) with respect to such a list of potential channels in theunlicensed frequency band, in such a scenario. For example, the UE mayperform one or more measurements (e.g., on interference/signalstrength/RSSI scans/any of various other channel condition metrics) onsome or all of the potential channels to determine channel conditionsfor those channels local to the UE, e.g., to confirm that those channelsare also relatively free of interference in the vicinity of the UE. Asanother example, the UE may have limits to its wireless communicationcapabilities, as a result of which it may not be possible to performcommunications according to the first wireless communication technologyon a particular frequency band, potentially including one or more of thepotential channels indicated by the BS. Thus, the UE 106 might providechannel condition information, a pruned (or unpruned) list of supportedchannels, a list of unsupported channels, and/or any of various otherforms of feedback to the BS with respect to the list of potentialchannels in the unlicensed frequency band.

Once any scanning/channel measurements have been performed by the BS,and possibly based additionally on any feedback received from the UE,then the BS 102 may select the frequency channel in the unlicensedfrequency band on which to establish the cell. The selection may bebased on one or more of the scanning/channel measurements, any feedbackreceived from the UE, and/or network resource allocation considerations(e.g., known loading/use of network controlled communications, resourceavailability, etc.), among various possibilities.

If the cell in the unlicensed frequency band is a secondary cell in acarrier aggregation scheme, the BS may activate the secondary carrier byproviding an indication the UE to establish the secondary carrier on thesecond channel, e.g., via a configuration message (such as a “Scell Add”configuration message in LTE) transmitted on the primary carrier.Alternatively, if the cell in the unlicensed frequency band is astand-alone cell, the cell may be established between the BS and the UEas an initial cell selection (e.g., in which the UE attaches to thecell) or via a (e.g., network guided) cell-reselection process.

In 704, a downlink communication with the UE may be scheduled on thecell in the unlicensed frequency band. Note that at least in someinstances, the BS may perform an energy sensing operation to ensure themedium availability before performing the resource scheduling. The BSmay, for example, only schedule the downlink communication if the mediumis available; if the medium is busy, the scheduling may be delayed(e.g., until such a time as the medium is available).

As one possibility, an indication of the scheduled downlinkcommunication may be provided to the UE by way of a control channel(e.g., the PDCCH in LTE) provided as part of the cell.

Alternatively, as previously noted, in some instances (e.g., if the cellin the unlicensed frequency band is a secondary cell as part of acarrier aggregation scheme) the cellular network may utilizecross-carrier scheduling to schedule/allocate secondary cell resourcesto the UE. For example, in such an instance the BS may providescheduling information (e.g., uplink and/or downlink grants) forscheduling secondary cell resources to the UE via the primary carrier.Using cross-carrier scheduling in such a scenario may enable the networkto keep control communications on the licensed frequency band, which aspreviously noted with respect to FIG. 6, may be subject to less (or atleast less external) interference than the unlicensed frequency band.

In 706, in order to reserve the medium, the BS may transmit a Wi-Fisignal, or a hybrid Wi-Fi/cellular signal on the frequency channel (oron a Wi-Fi channel corresponding in frequency) of the cell in theunlicensed frequency band in conjunction with the scheduled downlinkcommunication. As previously noted, the BS may be equipped with (orcommunicatively coupled with) Wi-Fi communication circuitry, e.g., tofacilitate transmission of such a signal by the BS, among variousreasons. Alternatively, note that the Wi-Fi signal may be incorporatedto the LTE protocol, if desired; for example, it might be appended tothe LTE transmission. Note further that in such a case the BS might notneed a Wi-Fi transceiver, as the Wi-Fi or hybrid Wi-Fi/cellular signalmay be generated and transmitted by LTE circuitry and transceiver of theBS.

Note that if desired, this Wi-Fi or hybrid Wi-Fi/cellular signal couldbe used for unlicensed LTE frequency and timing tracking as well as formedium reservation.

The Wi-Fi signal may indicate a length of the scheduled downlinkcommunication using Wi-Fi signaling. For example, as one possibility,the Wi-Fi signal may include a Wi-Fi preamble and signal (SIG) fieldindicating a number of orthogonal frequency division multiplexing (OFDM)symbols corresponding to the length of the scheduled downlinkcommunication. More generally, the Wi-Fi signal may be in anyappropriate format which is specified by the Wi-Fi wirelesscommunication technology and/or recognized by Wi-Fi devices. In someinstances, the Wi-Fi signal may also or alternatively include a Wi-Firequest-to-send (RTS) and/or clear-to-send (CTS) message. As a stillfurther possibility (e.g., for cellular frequency/timing tracking), thesignal may contain a LTE based discovery reference signal CSI-RS, ifdesired.

Transmitting the Wi-Fi signal or hybrid signal indicating the length ofthe scheduled downlink communication may help prevent Wi-Fi devices fromtransmitting during the scheduled downlink communication, which couldcause interference. For example, any Wi-Fi devices detecting anddecoding the Wi-Fi signal transmitted by the BS may determine that themedium will be occupied for the indicated length of time/number of OFDMsymbols, and accordingly refrain from transmitting until the indicatedlength of time/number of OFDM symbols has passed, even if the downlinkcommunication itself (which may be performed according to LTE or anotherRAT which Wi-Fi radios may not be capable of detecting and/or decoding)is not detected by the Wi-Fi devices' PHY sensing mechanisms.

The Wi-Fi or hybrid signal may be transmitted prior to, or possiblypartially or entirely temporally overlapping with, the scheduleddownlink communication. Note, however, that if any portion of the Wi-Fisignal is transmitted concurrently with the scheduled downlinkcommunication, it may be helpful to deploy interferencemanagement/mitigation techniques to avoid interference to the scheduleddownlink communication caused by transmission of the Wi-Fi signal.

Note that the length indicated by the Wi-Fi signal may include all orjust a portion of a scheduled downlink communication. For example, if adownlink communication is expected (e.g., based on RRC buffer levels inan LTE scenario) to span multiple transmission time intervals, a Wi-Fisignal indicating the expected (e.g., plural) number of TTIs could betransmitted at the beginning of that set of TTIs. Alternatively, a Wi-Fisignal indicating a length corresponding to a single TTI could beprovided in conjunction with each TTI in which downlink communication isscheduled.

In addition to generating and transmitting the Wi-Fi or hybrid signal toavoid interference to the scheduled downlink communication, note that atleast in some instances the BS (and possibly the UE) may also monitorthe wireless medium of the cell in the unlicensed frequency band forWi-Fi signals prior to performing the scheduled downlink communication.For example, in some instances other Wi-Fi devices or cellular devices(e.g., other BSs or UEs) configured to operate in the unlicensedfrequency band may already be communicating, or may attempt tocommunicate, at the same time as the BS and the UE. Accordingly, the BS(and possibly the UE) may monitor or listen to the wireless medium inorder to determine whether it is busy (occupied) or free (unoccupied).If the medium is busy, the BS may delay (not perform) the scheduleddownlink communication in order to avoid interfering (causing acollision) with the detected use of the medium, while if the medium isfree, the BS may go ahead with the scheduled downlink communication.

In 708, the scheduled downlink communication may be performed. This mayinclude communication of downlink data from the BS to the UE via thecell on the unlicensed frequency band according to the schedulingconfigured by the BS. The data communicated may include any of a varietyof types of data, including user data (e.g., application data for aweb-browser, mapping application, email client, media streamingapplication, game, or any of various other types of applications),background data (e.g., software updates), etc.

Note that in some instances, such as certain carrier aggregationschemes, a secondary cell may not be used for uplink communications.However, if the cell in the unlicensed frequency band is used for uplinkcommunications (e.g., because it is a stand-alone or primary cell, or itis a secondary cell in a carrier aggregation scheme in which uplinkcommunication is enabled), similar techniques may be implemented foruplink communication from a UE to a BS, if desired. Steps 710-714 ofFIG. 7 relate to such techniques.

In 710, an uplink communication via the cell may be scheduled betweenthe BS and the UE. Similar to the scheduled downlink communication, anindication of the scheduled uplink communication may be provided to theUE, for example by way of a control channel (e.g., the PDCCH in LTE)provided as part of the cell. Alternatively, (e.g., if the cell in theunlicensed frequency band is a secondary cell as part of a carrieraggregation scheme) cross-carrier scheduling may be used, such that theindication of the scheduled uplink communication may be provided via adifferent (e.g., the primary) cell.

In 712, the UE may transmit a Wi-Fi signal or hybrid Wi-Fi/cellularsignal on the frequency channel (or on a Wi-Fi channel corresponding infrequency) of the cell in the unlicensed frequency band in conjunctionwith the scheduled uplink communication. The UE may be equipped withWi-Fi communication circuitry, e.g., to facilitate transmission of sucha signal by the UE, among various reasons; alternatively, and assimilarly noted above for the case of the BS, if the signal is part ofthe LTE protocol, the Wi-Fi or hybrid Wi-Fi/cellular signal may begenerated and transmitted by cellular (e.g., LTE) circuitry of the UE,in which case a Wi-Fi transceiver might not be needed by the UE for thispurpose. Similar to the Wi-Fi signal or hybrid Wi-Fi/cellular signaltransmitted by the BS in step 706, this Wi-Fi or hybrid Wi-Fi/cellularsignal could also be used for unlicensed LTE frequency and timingtracking as well as for medium reservation, if desired.

The Wi-Fi signal may indicate a length of the scheduled uplinkcommunication using Wi-Fi signaling. For example, as one possibility,the Wi-Fi signal may include a Wi-Fi preamble and signal fieldindicating a number of orthogonal frequency division multiplexing (OFDM)symbols corresponding to the length of the scheduled uplinkcommunication. More generally, as in the downlink scenario, the Wi-Fisignal may be in any appropriate format which is specified by the Wi-Fiwireless communication technology. In some instances, the Wi-Fi signalmay also or alternatively include a Wi-Fi request-to-send (RTS) and/orclear-to-send (CTS) message. The Wi-Fi signal may be transmitted priorto, or possibly partially or entirely temporally overlapping with, thescheduled uplink communication.

Note that much as in the case of the scheduled downlink communication,in the case of the scheduled uplink communication, it may also be thecase that in addition to generating and transmitting the Wi-Fi or hybridsignal to avoid interference to the scheduled uplink communication, theUE (and possibly the BS) may also monitor the wireless medium of thecell in the unlicensed frequency band for Wi-Fi signals prior toperforming the scheduled uplink communication. Thus, the UE (andpossibly the BS) may monitor or listen to the wireless medium in orderto determine whether it is busy or free. If the medium is busy, the UEmay delay the scheduled uplink communication in order to avoidinterfering with the detected use of the medium, while if the medium isfree, the UE may go ahead with the scheduled uplink communication.

In 714, the scheduled uplink communication may be performed. This mayinclude communication of uplink data from the UE to the BS via the cellon the unlicensed frequency band according to the scheduling configuredby the BS. The data communicated may include any of a variety of typesof data, including user data, background data, etc.

Thus, according to the scheme of FIG. 7, a BS and a UE may utilize Wi-Fisignaling to provide an indication of the length of scheduledcommunications via a cellular communication technology such as LTE on anunlicensed frequency band. Such techniques may facilitate efficientco-existence between Wi-Fi and a cellular communication technology whichimplements such techniques, as it may prevent conflicts between cellulardevices (e.g., BSs and UEs) and Wi-Fi radios which detect such Wi-Fisignaling indications of the length of scheduled cellular communicationsand which might otherwise attempt to transmit (and thus potentiallyinterfere) during such scheduled cellular communications.

Note additionally that elements of the method may be expanded and/orrepeated as desired such that any number of (uplink and/or downlink)cellular communications may be performed between a BS and a UE withprotection from interference provided by way of Wi-Fi signaling of thelength of such communications by the BS and/or the UE.

FIGS. 8-16—Additional Information

FIGS. 8-16 and the information provided herein below in conjunctiontherewith are provided by way of example of various considerations anddetails relating to possible systems in which the method of FIG. 7 maybe implemented, and are not intended to be limiting to the disclosure asa whole. Numerous variations and alternatives to the details providedherein below are possible and should be considered within the scope ofthe disclosure.

As previously noted, an operator of an LTE network may use a primarycarrier (Pcell) to schedule LTE data in a normal way, and a secondcarrier (Scell) may be added for communications through an LTE RAT in anISM Band or unlicensed Band. Such LTE Communications in the Scell wouldneed to avoid Wi-Fi interference in order to be successful.

As part of this, an LTE eNB providing a cell in an unlicensed band (an“LTE-U eNB”) may pick a channel in an ISM band that has an acceptablelevel of interference on which to provide the cell. Furthermore, it maybe desirable to provide a way for the LTE-U eNB to may make sure thatwhen communications are scheduled in that channel, there is no suddenbursty Wi-Fi communication that will degrade the performance of thecommunication in LTE Scell.

As an additional consideration, it may be desirable for such an LTE-UeNB to have a muting scheme (On/Off mechanism) to allow Wi-Fi devices toaccess the channel without LTE interference. Furthermore, it may bedesirable to implement techniques which facilitate Wi-Fi devices abilityto detect LTE-U communications. For example, such muting mechanisms(LTE) and DFS mechanisms (Wi-Fi) may not be able to operate correctly ifWi-Fi devices/access points (APs) are not able to sense/detect LTE-Ucommunications efficiently.

In other words, broadly speaking, mechanisms to enable coexistencebetween Wi-Fi and LTE-U in unlicensed bands may be necessary in order toimplement such a scheme.

Wi-Fi may use a random access mechanism to schedule communications. Inaddition, Wi-Fi includes a mechanism to control contention on thechannel medium. PHY sensing in 802.11 may allow a Wi-Fi device to detectthe preamble and the signal field in the PHY frame structure, and tosense Wi-Fi communications that have an RSSI between −82 dBm and −62dBM. If the medium is busy (e.g., as determined based on the PHY sensingof the preamble and the signal field and/or the signal strength of Wi-Ficommunications), the Wi-Fi device may wait until the currenttransmission is finished. The length which the Wi-Fi device waits caneither be based on/detected from the MAC network allocation vector (NAV)value (which may give the duration including the ACK) or the preambleand signal field (which may indicate the number of OFDM symbols for datatransmission, but may not contain the length of the ACK signal).

Such existing Wi-Fi contention and random access control mechanisms maybe leveraged to also facilitate efficient LTE and Wi-Fi co-existence.For example, a LTE-U eNB may be equipped with a Wi-Fi device (an accesspoint transceiver and BB chip). Note that as an additional possibility,in some instances an eNB may be equipped with a chipset specificallyconfigured for LTE use in unlicensed spectrum, which may include a Wi-Ficapability module, which may avoid the need for a separate Wi-Fichipset. FIG. 8 illustrates such an exemplary “LTE-U access point”,according to some embodiments. As shown, such a device may include aLTE-U transceiver capable of transmitting and receiving LTE-U data, aswell as a Wi-Fi capability module, which may provide partial or fullWi-Fi communication capabilities and may enable the LTE-U AP to transmitWi-Fi signals and/or hybrid Wi-Fi/LTE signals (e.g., preambles) formedium reservation, timing and/or frequency tracking (e.g., discoveryreference signals or DRS), and/or other purposes.

Thus, at least in some instances, a Wi-Fi module or device (which may beany combination of hardware, software, firmware, etc.) may be able toscan all Wi-Fi channels in the band of interest and report their RSSIand link quality metrics to the LTE-U eNB/AP. Once these measurementsare available at the LTE eNB, it may determine a list of potentialchannels that are not “polluted” by Wi-Fi communications in order toestablish LTE communications in Scell.

Wi-Fi channel measurements may be performed once (e.g., initially) topopulate a list of “good” Wi-Fi channels, and can also/alternatively beperformed periodically after or before every scheduled datacommunication to make sure that the conditions are still favorable for asuccessful LTE communication.

To further facilitate co-existence, the LTE-U eNB may be capable ofoperating using an On/Off mode. For example, the LTE-U eNB mighttransmit for a period of time (which may be statically defined by the3GPP specification documents, semi-statically defined by networkconfiguration, or dynamically determined based on interference, trafficload, etc.) and then go mute/silent for another period. The lengths oftime during which the LTE-U eNB is ‘on’ and ‘off’ may be any of variouslength of time, and may be equal or unequal. For example, each ‘on’periods and/or each ‘off’ period might be 10 ms, 15 ms, 20 ms, 30 ms, 40ms, or any other desired value.

To enable the Wi-Fi devices and Wi-Fi APs to sense LTE-U communications,and since the LTE-U eNB is equipped with a Wi-Fi device or module, aLTE-U eNB may transmit a Wi-Fi preamble+signal field before scheduling acommunication in the Scell.

The preamble+signal field may be transmitted ahead of any scheduledLTE-U transmission, and repeated as necessary. For example, thepreamble+signal could be sent prior to of each TTI (which may have aduration of lms) and the number of Wi-Fi OFDM symbols indicated in thesignal field may correspond to lms. Alternatively, the preamble andsignal transmission may temporally overlap with (e.g., the beginning of)the TTI to make sure Wi-Fi devices are not accessing the medium.

The frequency at which the preamble+signal field is sent may be adjustedto the typical length of a transmission in Wi-Fi (e.g., a few ms).Further Wi-Fi preamble+signal transmissions may be performed(retransmitted) by the LTE-U eNB based on the length of data put in theSIG field (i.e., the number of OFDM symbols indicated), if further LTE-Utransmissions are scheduled. This may restrain any Wi-Fi device/AP fromaccessing the medium/channel and may guarantee or at least improve thelikelihood of a clear channel for Scell LTE communication. When LTE-U isoff, a Wi-Fi device not detecting any preamble may be able to access thechannel.

FIGS. 9-10 illustrate possible transmission schemes. It should be notedthat block sizes are not drawn to scale with respect to the timeduration of those blocks in the illustrated schemes of FIGS. 9-10.

FIG. 9 illustrates a scheme in which preamble 902, 908 and signal 904,910 fields may be transmitted prior to LTE-U communications (e.g., TTIs906, 912) by a Wi-Fi device of an LTE-U eNB, and in which thepreamble+signal field indicates a transmission length (i.e., a number ofOFDM symbols) corresponding to one or more TTIs. Such a scheme may bebeneficial, for example, in a stand-alone LTE-U cell in which thepreamble+signal field transmission represents overhead during which noLTE communications are performed.

Alternatively, in case multiple TTIs are scheduled in an LTE-U celladjacent to each other, instead of sending a single preamble+signaltransmission containing information indicating that the length of thescheduled data transmission is multiple ms (which may not correspond torealistic data transmission lengths for Wi-Fi, whose averagetransmission may be on the order of 3 ms), the LTE-U eNB may use thePDCCH OFDM symbols of each TTI to trigger the Wi-Fi entity to send thepreamble+sig. FIG. 10 illustrates a such scheme.

Such a scheme may be convenient for carrier aggregation implementationsin which cross-carrier scheduling is used, such that the Pcell is usedto send control/scheduling information for both the Pcell and the Scell;in such a case, the portion of the LTE frame structure dedicated to thePDCCH on the Scell may be empty (empty PDCCH symbols 1002, 1010, 1018),and use of that timeframe to transmit the preamble 1004, 1012, 1020 andsignal 1006, 1014, 1022 fields on a per TTI 1008, 1016, 1024 basis maynot interfere with LTE communications. For example, in many instances,the PDCCH may occupy 3 OFDM symbols, which may approximately correspondto 215 μs. This may be sufficient to accommodate the Preamble+signalfield (which may be approximately 20 μs), and also RTS/CTS signaling ifdesired or needed.

It may be possible, and in many cases desirable, for any LTE-U devices(e.g., including user devices) that support communication in unlicensedspectrum to use similar mechanisms. For example, in the case of astand-alone LTE-U eNB, LTE-U devices may perform uplink (UL)communications in addition to downlink (DL) communications.

Because of inter-device coexistence issues (e.g., as specified by 3GPP),the LTE-U devices may use a coexistence interface 1102, 1104 (e.g., asillustrated in FIG. 11) to send commands from an LTE-U-WLAN coexistencemodule 1110 in their LTE transceivers 1106 to a module 1112 in theirWi-Fi transceivers 1108 to generate and transmit a Wi-Fi preamble. Thisinterface may be able to account for/correct any timing differencebetween the LTE transceiver 1106 and Wi-Fi transceiver 1108.Alternatively, in an integrated IC (e.g., a combined LTE+Wi-Fi chip),both transceivers may be driven by the same clock, which may effectivelymitigate or altogether negate any potential timing issues.

FIGS. 12-16 illustrates aspects of the Wi-Fi channel sensing mechanismwhich may be leveraged according to the techniques described hereinabove. As shown in FIG. 12, information regarding the length of atransmitted frame may be provided in the PHY header of the frame. Basedon such information, and standard/specified interframe spaces (e.g, DCFinterframe space (DIFS) and short interframe space (SIFS)) andAcknowledgement lengths, a Wi-Fi device may be able to determine alength of time for which the medium will be occupied. This may enablethe Wi-Fi device to conserve power (e.g., by sleeping for the period oftime during which the medium will be occupied) and prevent conflictingmedium usage.

As shown in FIG. 13, once such a length of time has passed, a contentionwindow (CW) may begin. Any Wi-Fi devices desiring to transmit at thattime may wait until a randomly selected slot within the contentionwindow before seizing the medium and beginning its transmission. If themedium is occupied (as may be detected by PHY sensing) at the time aWi-Fi device's random backoff period ends (e.g., because another Wi-Fidevice desiring to transmit had a shorter random backoff period/selectedan earlier slot), the Wi-Fi device may again defer medium control andwait for the next contention window.

As shown in FIG. 14, subsequent retransmission attempts (i.e., after atransmission fails, for example due to medium conflict) may be subjectto exponentially expanded contention windows. Increasing the number ofslots in the contention window may decrease the likelihood of accessconflicts (as there may be a greater number of slots from which tochoose by Wi-Fi devices desiring medium access), and thus increase thelikelihood of a successful transmission.

FIG. 15 illustrates the distributed coordination function (DCF) used byWi-Fi, which includes the use of network allocation vector protection,contention windows, and random backoff periods as illustrated anddescribed individually with respect to FIGS. 12-14.

FIG. 16 illustrates an exemplary Wi-Fi physical layer protocol data unit(PPDU or PHY packet). As shown, a typical Wi-Fi PHY packet may include a12 symbol PLCP preamble, a one symbol signal field, and then a variablenumber of symbols of data. The preamble may typically extend forapproximately 16 μs, and may be used for signal detection, automaticgain control, diversity selection, course frequency offset estimation,timing synchronization, and channel and fine frequency offsetestimation. The signal field may typically extend for approximately 4μs, and may include portions indicating a coding rate used for the dataportion of the communication and indicating a number of OFDM symbols,along with parity and tail bits. The signal field may use binary phaseshift keying (BPSK) and a rate of 1/2 as its modulation and codingscheme (or more generally as according to the Wi-Fi specification). Thedata field may typically include data communicated using a number ofsymbols indicated by the signal field, which may be coded at the rateindicated by the signal field.

However, whereas a typical Wi-Fi communication frame may actuallyinclude Wi-Fi communication of data subsequent to the preamble andsignal field according to the parameters indicated in the signal field,an LTE-U device (e.g., BS or UE) may transmit only the preamble andsignal field using Wi-Fi communication according to the techniquesdescribed herein, and follow such Wi-Fi communication with LTE-Ucommunication instead of Wi-Fi communication. Thus, while the LTE-Ucommunication may not literally match the coding rate and number ofsymbols indicated in the signal field, the length of time used for thefollowing LTE-U communication may match the length of time which wouldbe used transmit the number of symbols indicated in the signal field atthe coding rate indicated in the signal field.

In the following further exemplary embodiments of the disclosure arepresented.

A first exemplary embodiment includes an apparatus comprising means forperforming Wi-Fi signaling in conjunction with cellular communication inunlicensed frequency bands. The apparatus may include means forestablishing an cell with a wireless user equipment (UE) device on afrequency channel in an unlicensed frequency band. The apparatus mayfurther include means for scheduling a cellular communication with theUE device. Additionally, the apparatus may include means fortransmitting a Wi-Fi signal on the frequency channel in conjunction withthe scheduled cellular communication, wherein the Wi-Fi signal indicatesa length of the scheduled cellular communication using Wi-Fi signaling.Further, the apparatus may include means for performing the scheduledcellular communication with the UE device via the cell.

A second exemplary embodiment includes a computer program withinstructions for performing a method for performing Wi-Fi signaling inconjunction with cellular communication in unlicensed frequency bands.The method may include establishing an cell with a UE device on afrequency channel in an unlicensed frequency band. The method mayfurther include scheduling a cellular communication with the UE device.Additionally, the method may include transmitting a Wi-Fi signal on thefrequency channel in conjunction with the scheduled cellularcommunication, wherein the Wi-Fi signal indicates a length of thescheduled cellular communication using Wi-Fi signaling. Further, themethod may include performing the scheduled cellular communication withthe UE device via the cell.

In either or both of the above-described exemplary embodiments, theWi-Fi signal may comprise a Wi-Fi preamble and signal field indicating anumber of orthogonal frequency division multiplexing (OFDM) symbolscorresponding to the length of the scheduled cellular communication. TheWi-Fi preamble and signal field may indicate a Wi-Fi communicationhaving a length corresponding to the length of the scheduled cellularcommunication, where the indicated Wi-Fi communication is not performed.The signal field may indicate a number of orthogonal frequency divisionmultiplexing (OFDM) symbols and a coding rate of the indicated Wi-Ficommunication, wherein the number of OFDM symbols and the coding rateindicated correspond to a length of time of the scheduled cellularcommunication.

In any of the above-described exemplary embodiments, the cell may be asecondary cell in a carrier aggregation arrangement. The method may inthis case include, or the apparatus may include means for, establishinga primary cell in the carrier aggregation arrangement with the UE deviceon a frequency channel in a licensed frequency band and performingcellular control communications for both the primary cell and thesecondary cell via the primary cell.

In the just-described exemplary embodiment, scheduling the cellularcommunication with the UE device may be performed as part of thecellular control communications performed via the primary cell, andtransmitting the Wi-Fi signal on the frequency channel in the unlicensedfrequency band may be performed simultaneously with performing thecellular control communications via the primary cell.

Alternatively, cellular control communications may be performed via thecell, and scheduling the cellular communication with the UE device maybe performed as part of the cellular control communications performedvia the cell. In this case, transmitting the Wi-Fi signal on thefrequency channel in the unlicensed frequency band may be performedsimultaneously with or prior to performing the cellular controlcommunications via the cell.

In any of the above-described exemplary embodiments, the scheduled LTEcommunication comprises one transmission time interval (TTI) accordingto LTE. Alternatively, in any of the above-described exemplaryembodiments, the scheduled LTE communication comprises multiple TTIsaccording to LTE.

In any of the above-described exemplary embodiments, the cellularcommunications and cellular control communications may include LTEcommunications and LTE control communications.

In addition to the above-described exemplary embodiments, furtherembodiments of the present disclosure may be realized in any of variousforms. For example some embodiments may be realized as acomputer-implemented method, a computer-readable memory medium, or acomputer system. Other embodiments may be realized using one or morecustom-designed hardware devices such as ASICs. Still other embodimentsmay be realized using one or more programmable hardware elements such asFPGAs.

In some embodiments, a non-transitory computer-readable memory mediummay be configured so that it stores program instructions and/or data,where the program instructions, if executed by a computer system, causethe computer system to perform a method, e.g., any of a methodembodiments described herein, or, any combination of the methodembodiments described herein, or, any subset of any of the methodembodiments described herein, or, any combination of such subsets.

In some embodiments, a device (e.g., a UE 106) may be configured toinclude a processor (or a set of processors) and a memory medium, wherethe memory medium stores program instructions, where the processor isconfigured to read and execute the program instructions from the memorymedium, where the program instructions are executable to implement anyof the various method embodiments described herein (or, any combinationof the method embodiments described herein, or, any subset of any of themethod embodiments described herein, or, any combination of suchsubsets). The device may be realized in any of various forms.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

What is claimed is:
 1. A method for operating a wireless user equipment(UE) device, the method comprising: establishing a primary cellaccording to long term evolution (LTE) with a cellular base station on afrequency channel in a licensed frequency band; establishing a secondarycell according to LTE with the cellular base station on a frequencychannel in an unlicensed frequency band; receiving an indication of ascheduled LTE downlink communication on the secondary cell from thecellular base station via the primary cell; prior to receiving thescheduled LTE downlink communication, receiving a discovery referencesignal (DRS) on the frequency channel in the unlicensed frequency band,wherein the DRS is included in a hybrid Wi-Fi/LTE signal comprising aWi-Fi preamble and the DRS, wherein the DRS comprises an LTE basedsignal; performing one or more of cellular timing and frequency trackingfor the unlicensed frequency band using the DRS; and receiving thescheduled LTE downlink communication.
 2. The method of claim 1, whereinthe DRS is an LTE based signal.
 3. The method of claim 1, wherein theDRS comprises a channel state information reference signal (CSI-RS). 4.The method of claim 1, wherein the DRS is comprised in the hybridWi-Fi/LTE signal, wherein the hybrid Wi-Fi/LTE signal further comprisesa Wi-Fi signal indicating a length of the scheduled LTE downlinkcommunication.
 5. The method of claim 1, further comprising: receivingcellular control communications for both the primary cell and thesecondary cell via the primary cell.
 6. The method of claim 1, whereinthe hybrid Wi-Fi/LTE signal further comprises a request-to-send (RTS)signal.
 7. The method of claim 1, wherein the hybrid Wi-Fi/LTE signalfurther comprises a clear-to-send (CTS) signal.
 8. An apparatusconfigured for inclusion in a wireless user equipment (UE) device,comprising: one or more processing elements, wherein the one or moreprocessing elements are configured to: establish a primary cellaccording to long term evolution (LTE) with a cellular base station on afrequency channel in a licensed frequency band; establish a secondarycell according to LTE with the cellular base station on a frequencychannel in an unlicensed frequency band; receive an indication of ascheduled LTE downlink communication on the secondary cell from thecellular base station via the primary cell; prior to receiving thescheduled LTE downlink communication, receive a discovery referencesignal (DRS) on the frequency channel in the unlicensed frequency band,wherein the DRS is included in a hybrid Wi-Fi/LTE signal comprising aWi-Fi preamble and the DRS, wherein the DRS comprises an LTE basedsignal; perform one or more of cellular timing and frequency trackingfor the unlicensed frequency band using the DRS; and receive thescheduled LTE downlink communication.
 9. The apparatus of claim 8,wherein the DRS is an LTE based signal.
 10. The apparatus of claim 8,wherein the DRS comprises a channel state information reference signal(CSI-RS).
 11. The apparatus of claim 8, wherein the DRS is comprised inthe hybrid Wi-Fi/LTE signal, wherein the hybrid Wi-Fi/LTE signal furthercomprises a Wi-Fi signal indicating a length of the scheduled LTEdownlink communication.
 12. The apparatus of claim 8, wherein the one ormore processing elements are further configured to: receive cellularcontrol communications for both the primary cell and the secondary cellvia the primary cell.
 13. The apparatus of claim 8, wherein the hybridWi-Fi/LTE signal further comprises a request-to-send (RTS) signal. 14.The apparatus of claim 8, wherein the hybrid Wi-Fi/LTE signal furthercomprises a clear-to-send (CTS) signal.
 15. A method for operating abase station, the method comprising: establishing a primary cellaccording to long term evolution (LTE) with a mobile station on afrequency channel in a licensed frequency band; establishing a secondarycell according to LTE with the mobile station on a frequency channel inan unlicensed frequency band; scheduling a cellular communication withthe mobile station on the secondary cell via the primary cell; priorperforming the scheduled cellular communication with the mobile station,transmitting a discovery reference signal (DRS) on the frequency channelin the unlicensed frequency band, wherein the DRS is configured for oneor more of cellular timing and frequency tracking, wherein the DRS isincluded in a hybrid Wi-Fi/LTE signal comprising a Wi-Fi preamble andthe DRS, wherein the DRS comprises an LTE based signal; and performingthe scheduled cellular communication.
 16. The method of claim 15,wherein the DRS is an LTE based signal.
 17. The method of claim 15,wherein the DRS comprises a channel state information reference signal(CSI-RS).
 18. The method of claim 15, wherein the DRS is comprised inthe hybrid Wi-Fi/LTE signal, wherein the hybrid Wi-Fi/LTE signal furthercomprises a Wi-Fi signal indicating a length of the scheduled LTEdownlink communication.
 19. The method of claim 15, further comprising:transmitting cellular control communications for both the primary celland the secondary cell via the primary cell.
 20. The method of claim 15,wherein the hybrid Wi-Fi/LTE signal further comprises a request-to-send(RTS) or a clear-to-send (CTS) signal.